What is a Drought?

Built to Bend: The Engineering of Resilience #1

The need to learn more about drought

Drought has always been one of the main threats to our society. Drought is also said to affect more people than any other natural disaster¹. This phenomenon is also kind of hard to identify and mitigate.

Drought also differs from other natural hazards for these three different reason²:

1. Drought is not a sudden natural hazard; it is mostly referred to as a creeping phenomenon.
2. There are no precise and universally accepted definitions of droughts; this lack of consensus possibly raises confusion about the existence or the severity of a drought.
3. Drought impacts are nonstructural; these impacts are different from other natural hazards.

This ambiguity in definition serves as the catalyst for today’s discussion. In the long story of humankind, there are, for sure, some prominent researchers who use their expertise to address this problem.

Drought is not a new phenomenon in this long story of humankind. The Indus River Valley Civilization, the Mediterranean Bronze Age Civilizations, and the South- and Meso-American Civilizations are some of the examples of civilizations that were affected by drought (and eventually collapse?).

Mishra (2010) stated that there are two reasons why research on droughts is very important, which are: (1) Impact of climate change on droughts; and (2) Impact of droughts around the globe during recent decades. These are the topics for our next conversation.

Defining and classifying drought

The process of defining drought can be traced back to 1887, when it was introduced in Britain, to be exact, in Britain Rainfall, which defined drought from the period of the lack of rain. These are absolute droughts, partial droughts, and an engineer’s drought⁴.

We did have a disagreement in defining the concept of drought; the examples are in Brazil and in Australia. What we can agree upon is the fact that they originate from a deficiency of precipitation that results in water shortage for some activity or for some group⁴. But this is only a conceptual definition, and it’s hard to use it for drought assessment.

The effort to emphasize the definition of drought as an operational definition is well discussed in the article written by Donald A. Wilhite (1985). By clustering the definition identified by Subrahmanyam, he then defined it into: meteorological drought, agricultural drought, hydrologic drought, and socio-economic drought⁴.

Meteorological Drought

Meteorological droughts are the most prevalent and often site-specific. Which means every country or region has its own way to define it, either from the limit of precipitation or the period of days without rain.

In Indonesia, the meteorological drought is based on the period of days without rain, the probability of daily precipitation, and the Standardized Precipitation Index (SPI)⁵.

Agricultural Drought

Agricultural drought reflects the impact of meteorological characteristics on farming outcomes. This also accounts for the susceptibility of crops at different stages of crop development.

The US Department of Agriculture has adopted the Crop Moisture Index (CMI), which was developed from the Palmer Drought Severity Index (PDSI).

In Indonesia, we already have scientists who developed the Indeks Dampak Kekeringan Padi (IDKP) using observed crop dryness data⁶. With the importance of El Niño in the climatic environment of Indonesia, the Ministry of Agriculture also stated the need for El Niño Southern Oscillation (ENSO) prediction as one of the supporting data⁷.

Hydrologic Drought

Definitions of hydrologic drought, different from other droughts, are not concerned with the meteorological explanation of the event. This definition is concerned with the effects of dry spells on surface or subsurface water levels.

This drought uses PDSI as the indicator, with the Surface Water Supply Index (SWSI) as the complementary assessment. In Indonesia, however, the Standardized Runoff Index (SRI) is the most used method for the assessment of hydrological drought.

Socio-economic Drought

This is where the definitions of drought are closely related to our everyday life. This drought is usually associated with the supply and demand of some economic good. In this definition, drought only occurs when supply falls below the level of requirement, which is dependent upon the distribution of plant, animal and human populations, and more importantly, their lifestyle and their use of the land.

This is where humans use their engineering, their ability to bend, by using an artificial environment. Some prevail and exist till today, and some bend too much for their own good and eventually collapse. This is the true beauty of my long writing journey; this is the built-to-bend series.

Further Discussion

Defining a simple word such as drought, however, brings us to the journey of humankind. When we thought that a general definition was not good enough, people from around the world gave their best to define it. This can only be done when we recognize the lessons from the past.

This is only the start of much more discussion in the future. The long story of disaster and the ability of humans to make an artificial environment to adapt, to bend, and live side-by-side with it.

Bibliography

1. Coles, Neil A., and Saeid Eslamian. “Definition of drought.” Handbook of drought and water scarcity. CRC Press, 2017. 1–11.
2. Wilhite, Donald A., and Margie Buchanan-Smith. “Drought as hazard: understanding the natural and social context.” Drought and water crises: Science, technology, and management issues 3 (2005): 29.
3. Mishra, Ashok K., and Vijay P. Singh. “A review of drought concepts.” Journal of hydrology 391.1–2 (2010): 202–216.
4. Wilhite, Donald A., and Michael H. Glantz. “Understanding: the drought phenomenon: the role of definitions.” Water international 10.3 (1985): 111–120.
5. Badan Meteorologi, Klimatologi, dan Geofisika (2019). “Peraturan Kepala Badan Meteorologi, Klimatologi, dan Geofisika Republik Indonesia Nomor 9 Tahun 2019 tentang Penyediaan dan Penyebaran Peringatan Dini Iklim Ekstrim.”
6. Surmaini, Elza. “Pemantauan dan peringatan dini kekeringan pertanian di Indonesia.” Jurnal Sumberdaya Lahan 10.1 (2016).
7. Kementerian Pertanian (2018). “Peraturan Menteri Pertanian Republik Indonesia Nomor 39/Permentan/HM.130/8/2018 tentang Sistem Peringatan Dini dan Penanganan Dampak Perubahan Iklim pada Sektor Pertanian.”